The present disclosure relates to a rotary wing aircraft, and more particularly, to a rotary wing aircraft having a direct drive electric propulsion system.
Rotor blades of rotary-wing aircraft, such as co-axial rotor helicopters, typically create lift from a down-flow of air from above. During normal powered flight operations differential collective is used to provide a yawing moment in an expected direction. When the rotor is in an autorotative state, however, an up-flow of air is provided to the rotor, and the ability to generate torque, and therefore yawing moment by differential collective, and control of the aircraft is degraded. As a result, additional means of yaw control are typically provided in such aircraft. These means may include thrusters and/or a large rudder located at the back end of the helicopters. These additional means of yaw control increase cost, weight and complexity of the aircraft.